Wax compositions



2,988,528 WAX COMPOSITIONS John D. Tench and Arthur W. Taylor, ProspectPark, Pa., assignors to Sun Oil Company, Philadelphia, Pa., acorporation of New Jersey No Drawing. Filed Feb. 3, 1958, Ser. No.712,679 3 Claims. (Cl. 260-285) This invention relates to a new waxcomposition especially suitable for coating fibrous containers forliquids, such as paper cups.

Parafiin waxes have heretofore been employed for coating papercontainers designed to hold liquids, but such waxes suffer manyshortcomings. In order to overcome some of the difliculties,microcrystalline waxes and polymers, such as polyethylene, have beenincorporated therewith. Such compositions, however, have also beenunsatisfactory in one or more of the following: in pre senting anunsightly appearance, in obtaining poor coverage with subsequentsoftening when filled with liquids, in blocking at relatively lowtemperatures, and in requiring conditions during application to papercontainers which cannot be met with existing equipment.

An object of the present invention is to provide wax compositionsespecially suitable for coating fibrous containers for fluids. Aparticular object is to provide a wax composition eifcctive for coatingpaper containers for liquids, which imparts a pleasing appearance to theresulting article of manufacture, while obtaining good coverage and goodblocking characteristics, and which can be readily applied with existingequipment. A further object is to provide a process for the preparationof such wax composition.

It has now been found that by blending four components in certainamounts, a wax composition which achieves the above and other objects isobtained. The four components comprise twoparaffin waxes, amicrocrystalline wax and polyethylene, each of which must have specificproperties and must be used in certain amounts as hereinafter described;

As used herein, melting points for paratfin waxes are determined by ASTMD87-42 and for microcrystalline waxes. are determined by ASTM D'127-49,penetrations by ASTM D5-52 and viscosities (SUSSaybolt Universalseconds) by ASTM D446-53, unless otherwise stated.

The first paraffin wax must have a melting point of from 149 F. to 155F., a penetration (at 77 F.) of from about 9 to 15 and a viscosity (at210 F.) of from 42' to 46 SUS. On distillation, 5% of the wax shoulddistill at about 820 F. and 95% should be distilled at about 950 F. Thiswax is prepared from petroleum by distilling slack wax which may be fromthe dewaxing of lubricating oil, or from a topped, high Wax contentcrude petroleum, and collecting the fraction distilled between about 450F. to 565 F; at 2 mm. of mercury pressure. This distillate fraction isthen dissolved in a solvent such as a mixture of methyl ethyl ketone andbenzene at an elevated temperature. The resulting solution is thencooled to a temperature of from about 77 F. to 83 -F. and the Wax whichprecipitates at this temperature is separated such as by filtration.Advantageously the Wax is washed with the same material as used for thesolvent at the temperature of, precipitation, and the wax is thenseparated from the. solvent. The resulting Wax forms the first paraffinwax of the present composition.

The second paraffin Wax used in the present compositions must have amelting point. of from about 130 F. to 136 F., a penetration (at 77 F.)of from about 10 to 16 and a viscosity (at 210 F.) of from about 36 to40 SUS. On distillation, of the wax should distill at about 750 F. and95% should be distilled at about 820 States Patent 0 F. This wax isprepared from petroleum by distilling slack wax from the dewaxing oflubricating oil, or from a topped, high wax content crude petroleum, andcollecting the fraction distilled between about 390 F. and 475 F. at 2mm. of mercury pressure. This distillate fraction is dissolved in asolvent such as a mixture of methyl ethyl ketone and benzene at anelevated temperature and the resulting solution cooled to from 32 F. to37 F. The wax precipitated at this temperature is separated as byfiltration. Advantageously the wax is washed with the same material asused for the solvent, and after removal of the wash liquid, therecovered wax forms the second paraifin wax of the present composition.

The microcrystalline wax of the present composition must have a meltingpoint of from about 169 F. to 179 F., a penetration (at 77 F.) of fromabout 10 to 20 and a viscosity (at 210 F.) of from about 70 to SUS. Thiswax is prepared from petroleum by distilling slack wax from the dewaxingof lubricating oil toremove all material boiling above about 550 F. at 2mm. of mercury pressure. On distillation, about 5% of the residualmaterial should distill at about 560 F. at 2 mm. of mercury pressure,and about 40% should be distilled at about 640 F. at 2 mm. of mercurypressure. The residual material is dissolved in a solvent, such as amixture of methyl ethyl ketone and benzene, at an elevated temperatureand the resulting solution cooled to a temperature of from about 50 F.to 60 F. The wax precipitated by cooling to this temperature isseparated as by filtration. The resulting wax, after washing preferablywith the same material as used for the solvent at the temperature of theprecipitation, and removal of the solvent, is the microcrystalline waxused in the present composition.

The polyethylene employed in the invention should have a relatively lowmolecular weight, i.e., from about 1,000 to 10,000, and preferably hasan average molecular weight of about 2,000. The specific gravity of thepolyethylene should be about 0.92 and the melting point from about 206to 216 F. This polyethylene can be prepared by any means heretoforedescribed, such as by subjecting ethylene to elevated pressurespreferably with free radical producing catalyst such as benzoylperoxide.

As above stated, it is essential that the above-described components ofthe composition be used in specific amounts. The two parafiin waxes mustbe used in substantially identical quantities, and the individualquantities may vary from about 41% to 50% by weight of the finalcomposition. The amount of the microcrylstalline wax can be varied onlyfrom about 5% to 10% by weight and the polyethylene can be varied onlyfrom about 0.1% to 1.0% by weight. If the quantity of the lower meltingparafiin wax is below the stated range, poor coverage of the papercontainers results so that leakage of the container may occur, whereasif a quantity thereof above the stated range is used, blocking of thecoated articles is observed even at relatively low temperatures. If thequantity of the higher melting paraffin wax is below the stated range,the coated containers exhibit poor blocking characteristics in thatblocking is observed. even at relatively low temperatures whereas if thequantity thereof is above the stated range, the coated articles presentan unsightly appearance in that the surface exihibit serpentine lines,and poor gloss. If the quantity of microcrystalline wax is below thestated range, poor coverage and protection are obtained so that leakageis frequently observed, whereas if the quantity thereof is above thestated range, the composition cannot be worked on existing equipmentsince the temperature required for coating is too high. Polyethylene isan essential component in the amounts stated. If the amount used isbelow the stated range, poor coverage is obtained, and the surface waxtends to be brittle,

whereas if a quantity above the stated range is used, the waxcomposition cannot be used in existing equipment since the temperaturerequired for coating the articles is too high.

In addition to requiring critical amounts of each component, it appearsthat waxes having properties outside of the stated ranges for each waxcomponent cannot be used. For example, substituting a wax having amelting polnt of 127 F. for the lower melting paraffin wax defeats thepurposes of the invention in that the resulting composition exhibitspoor blocking characteristics, and hence is unsuitable for coating paperarticles. Likewise, substituting a higher melting paraffin havingproperties outside the ranges of those described for the higher meltingparaffin of the present invention, or substituting a differentmicrocrystalline wax for the one herein described, results in acomposition exhibiting one or more of the above-described difi'iculties.

In order to illustrate a specific embodiment of the present invention, aparafiin wax having a melting point of 151 F., a viscosity (at 210 F.)of 43.6 SUS and a penetration (at 77 F.) of 10 was prepared as abovedescribed. On distillation, of the wax distilled at 820 F. and 95%distilled at 950 F. Specifically, this wax was prepared by topping ahigh wax content crude petroleum to about 38% bottoms. The bottoms werecharged to a vacuum distillation operation, operating at 2 mm. ofmercury pressure and the fraction distilling between 450 F. and 565 F.was collected. This distillate fraction was dissolved in a solventconsisting of a mixture of about 60% methyl ethyl ketone and 40% benzeneat a temperature of about 180 F., about two parts by volume of solventper part of wax being used. The resulting solution was slowly cooled to80 F. and the wax precipitated at this temperature was separated byfiltering. The wax cake was washed with an additional quantity of thesolvent at a temperature of 80 F. and the wax recovered from thesolvent.

A second paraffin wax having a melting point of 134 F., a penetration(at 77 F.) of 12 and a viscosity (at 210 F.) of 38.1 was prepared asabove described. On distillation, 5% of the wax distilled at 750 F., and95% distilled at 820 F. Specifically, this wax was prepared by topping ahigh wax content crude petroleum to about 38% bottoms. The bottoms werecharged to a vacuum distillation operation which operated at 2 mm. ofmercury pressure and the fraction distilling between 390 F. and 475 F.was collected. This distillate fraction was dissolved in a solventconsisting of a mixture of about 60% methyl ethyl ketone and 40% benzeneat a temperature of about 180 F., about 4 parts by volume of solvent perpart of wax being used. The resulting solution was slowly cooled to 35F. and the wax precipitated at this temperature was separated byfiltering. The wax cake was washed with an additional quantity of thesolvent at a temperature of 35 F., and the wax was then recovered fromthe solvent.

A microcrystalline wax was prepared as above described. Themicrocrystalline wax had a melting point of 172 F., a penetration (at 77F.) of 17 and aviscosity (at 210 F.) of 78 SUS. On distillation, 5% ofthe wax was distilled at 910 F. and 41% was distilled at 1,020 F.Specifically, this wax was prepared by vacuum distilling slack wax fromthe dewaxing of lubricating oil at 2 mm. of mercury pressure to removematerials boiling above about 550 F., and collecting a residual fraction5% of which distilled at 560 F. (2 mm. of mercury pressure) and 40% ofwhich distilled at 640 F. (2 mm. of mercury pressure). This residualfraction was dissolved in a solvent consisting of a mixture of about 60%methyl ethyl ketone and 40% benzene at a temperature of about 190 F.,about 4.5 parts by volume of solvent per part of wax being used. Theresulting solution was slowly cooled to 55 F. and the wax precipitatedat this temperature was separated by filtering. The wax cake was washedwith an additional quantity of the solvent at a temperature of 55 F.,and the wax was then recovered from the solvent.

The two paraffin waxes were blended together with the microcrystallinewax by heating a mixture thereof to a temperature of about 200 F. withstirring. Polyethylene having a molecular weight of 2,000 and a specificgravity of 0.92 was added to the molten mixture with stirring and thestirring was continued until a homogeneous blend was obtained. Thequantities of components employed were such that the resultingcomposition contained 46.1% of the lower melting paraffin wax, 46.1% ofthe higher melting paraffin wax, 7.55% of the microcrystalline wax and0.25% of the polyethylene, the amounts being expressed as percent byweight. The resulting composition was employed in a commercial processfor coating paper cups designed for use in holding liquids such aswater. Application to the cups was made in existing equipment withoutobserving any difficulties. Good coverage was obtained, and theresulting coated article presented a pleasing appearance, exhibited ahigh gloss, did not block even at temperatures of F. and showed goodworking characteristics.

In preparing the wax constituents of the subject paraffin waxcomposition, the described operating variables must be observed in orderto secure the advantages of the invention. However, the solvent used fordissolution of the wax fractions can be varied somewhat and good resultsobtained. The described solvent, consisting of about equal parts byvolume of methyl ethyl ketone and benzene gives good results, but moreor less of the two constituents, say from 30% to 70% by volume ofbenzene can be used. Also, other solvents can replace methyl ethylketone or benzene. For example, toluene can be substituted for a portionof the benzene and good results obtained.

The invention claimed is:

1. A wax composition consisting essentially of (A) from 41% to 50% of aparaffin wax having a melting point of from 149 F. to 155 F., apenetration at 77 F. of from 9 to 15 and a viscosity at 210 F. of from42 to 46 SUS; (B) from 41% to 50% of a paraffin wax having a meltingpoint of from F. to 136 F., a penetration at 77 F. of from 10 to 16 anda viscosity at 210 F. of from 36 to 40 SUS; (C) from 5% to 10% of amicrocrystalline wax having a melting point of from 169 F. to 179 F., apenetration at 77 F. of from 10 to 20 and a viscosity at 210 F. of from70 to 85 SUS; and (D) from 0.1% to 1% of polyethylene having a molecularweight of from 1,000 to 10,000.

2. A wax composition according to claim 1 in which the paraflin wax of(A) and the paraflin wax of (B) are present in substantially the samequantities.

3. A container for holding liquids formed from a paper sheet materialand provided with an adherent moisture and liquid resistant coating,said coating being formed from the Wax composition of claim 1.

References Cited in the file of this patent UNITED STATES PATENTS2,551,087 Barnhart et a1. May 1, 1951 2,642,366 Rumberger June 16, 19532,728,735 Anderson Dec. 27, 1955 2,733,225 Smith Jan. 31, 1956 2,758,100Bailly et al. Aug. 7, 1956 2,791,570 Backlund May 7, 1957 2,808,382Jakaitis Oct. 1, 1957 2,828,219 Heiges et al. Mar. 25, 1958

1. A WAX COMPOSITION CONSISTING ESSENTIALLY OF (A) FROM 41% TO 50% OF A PARAFFIN WAX HAVING A MELTING POINT OF FROM 149*F. TO 155*F., A PENETRATION AT 77* F. OF FROM 9 TO 15 AND A VISCOSITY AT 210*F. OF FROM 42 TO 46 SUS, (B) FROM 41% TO 50% OF A PARAFFIN WAX HAVING A MELTING POINT OF FROM 130*F. TO 136*F., A PENETRATION AT 77*F. OF FROM 10 TO 16 AND A VISCOSITY AT 210*F. TO 179*F., PENETRATION AT 77*F. OF FROM 10 TO A MICROCRYSTALLINE WAX HAVING A MELTING POINT OF FROM 169*F. TO 179*F., A PENERATION AT 77*F. OF FROM 10 TO 20 AND A VISCOSITY AT 210*F. OF FROM 70 TO 85 SUS, AND (D) FROM 0.1% TO 1% OF POLYETHYLENE HAVING A MOLECULAR WEIGHT OF FROM 1,000 TO 10,000. 